Drug Monograph
Full clinical overview, indications, dosage references & safety notes.
Overview
Auranofin (Ridaura®) is an orally administered gold-containing immunosuppressive agent used in dogs and cats for selected immune-mediated disorders. Its veterinary use is limited and generally reserved for cases that are unresponsive to, or cannot tolerate, more conventional immunomodulatory therapies.
In small animal practice, auranofin is primarily used to treat idiopathic polyarthritis and pemphigus complex in dogs and cats. In cats, it has also been used anecdotally for other immune-mediated dermatologic and inflammatory conditions. Compared with injectable gold salts, auranofin is reported to be less toxic but may also be less efficacious.
Auranofin has also gained interest as an adjunctive therapy in canine osteosarcoma when added to standard-of-care treatment. Limited studies have shown a potential survival benefit in dogs, although clinical experience remains limited and use should be carefully weighed against potential risks and costs.
Mechanism of Action (MOA): Auranofin is an orally available gold salt with anti-inflammatory and immunomodulatory effects. Gold is taken up by macrophages, where it inhibits phagocytosis, lysosomal enzyme activity, histamine release, and prostaglandin production. Auranofin suppresses helper T-cell activity and may also inhibit cellular DNA, RNA, and protein synthesis. Its antineoplastic effects are thought to be related to inhibition of thioredoxin reductase and induction of apoptosis.
Use of auranofin requires careful patient selection and intensive monitoring due to the risk of gastrointestinal, renal, hepatic, and hematologic toxicity. Because published safety and efficacy data in dogs and cats are limited, auranofin should be considered a second- or third-line option in appropriately selected patients.
Indications
Auranofin is used in dogs and cats for selected immune-mediated diseases when conventional immunomodulatory therapies are ineffective or not tolerated. Due to limited published data and potential toxicity, its use should be reserved for carefully selected cases.
- Idiopathic polyarthritis (dogs and cats): Used as an immunosuppressive agent in patients that fail to respond to, or cannot tolerate, standard therapies such as glucocorticoids or azathioprine.
- Pemphigus complex (dogs and cats): Indicated for immune-mediated dermatologic disease, particularly in refractory cases or when adverse effects limit other treatment options.
- Immune-mediated dermatologic disease in cats: Anecdotally reported for conditions such as eosinophilic granuloma complex, plasma cell pododermatitis, and stomatitis when conventional therapies are unsuccessful.
- Adjunctive treatment for osteosarcoma (dogs): Used in combination with standard-of-care therapy (e.g., surgery and chemotherapy) based on limited evidence suggesting improved survival in selected patients.
Dosage (Reference)
Dog
In dogs, all uses of auranofin are extra-label. Therapy should be reserved for patients that are unresponsive to, or cannot tolerate, conventional immunomodulatory drugs. Close laboratory monitoring is mandatory.
| Clinical use | Route | Dose | Notes |
|---|---|---|---|
| Immune-mediated skin disease / polyarthritis | PO | 0.05–0.2 mg/kg every 12 hours |
Maximum total dose: 9 mg per dog per day (NOT mg/kg). Often used with glucocorticoids. Allow a 4-week washout after discontinuing azathioprine. |
| Adjunct therapy for osteosarcoma | PO |
6 mg/dog every 3 days (<15 kg) 9 mg/dog every 3 days (>15 kg) |
Fixed-dose regimen (NOT mg/kg). Used in combination with standard therapy (e.g., surgery and carboplatin). |
• A lag period of 6–12 weeks may occur before clinical response is seen.
• If remission is achieved, pulse therapy (1–2 mg/kg PO every other week for 1 month, then once monthly) may be attempted.
• Consider discontinuation after 6 months of sustained remission.
Cat
In cats, auranofin is used extra-label for immune-mediated dermatologic and inflammatory diseases. Accurate dosing is critical and compounding is often required.
| Clinical use | Route | Dose | Notes |
|---|---|---|---|
| Immune-mediated skin disease | PO | 0.2–0.3 mg/kg every 12 hours |
Compounding usually required for accurate dosing. Used for conditions such as pemphigus complex, eosinophilic granuloma complex, plasma cell pododermatitis, and stomatitis. |
• Clinical response may take several weeks to months.
• Close monitoring for gastrointestinal and hematologic toxicity is essential.
• Dose adjustments or discontinuation may be required if adverse effects develop.
Warnings & Precautions
Auranofin is a gold-containing immunosuppressive agent with a narrow margin of safety in dogs and cats. Its use requires careful case selection, informed client consent, and intensive monitoring throughout therapy.
- Reserved use only: Auranofin should be used only when less toxic and less expensive immunomodulatory therapies (e.g., glucocorticoids, azathioprine) are ineffective or not tolerated.
- Systemic lupus erythematosus: Contraindicated, as gold salts may exacerbate disease activity.
- Hypersensitivity to gold: Contraindicated in animals with a known history of adverse reactions to gold-containing products.
- Bone marrow suppression: Do not use in animals with pre-existing bone marrow suppression or in those receiving other myelosuppressive drugs (e.g., azathioprine, cyclophosphamide).
- Hematologic toxicity: Dose-dependent immune-mediated thrombocytopenia, hemolytic anemia, and leukopenia may occur; discontinue therapy and initiate corticosteroids if immune-mediated reactions develop.
- Gastrointestinal toxicity: Diarrhea is common and dose dependent, particularly in dogs; signs often improve with dose reduction or drug discontinuation.
- Renal effects: Proteinuria may develop; monitor renal function and urinalysis regularly.
- Hepatic toxicity: Hepatotoxicity has been reported; use cautiously in animals with pre-existing liver disease.
- Dermatologic and mucosal reactions: Severe skin reactions, including toxic epidermal necrolysis, as well as corneal and oral ulcers, have been associated with therapy.
- Pregnancy and lactation: Contraindicated unless potential maternal benefits clearly outweigh the risks to offspring.
- Client counseling: Owners must be informed about delayed onset of effect, high cost, need for compounding, frequent laboratory monitoring, and potential for serious adverse effects.
Drug Interactions
Clinically important drug interactions with auranofin in dogs and cats are primarily related to additive immunosuppression or increased risk of hematologic and renal toxicity. Careful risk–benefit assessment and enhanced monitoring are required when combining auranofin with the following agents.
- Antimalarial drugs (e.g., primaquine, quinacrine): Concurrent use with gold salts is not recommended due to an increased risk of hematologic and renal toxicity.
- Immunosuppressive agents (e.g., azathioprine, high-dose corticosteroids, leflunomide, pyrimethamine): Safety of combined use has not been established; additive immunosuppression and toxicity are possible. Use with caution and monitor closely.
- Myelosuppressive agents (e.g., chlorambucil, chloramphenicol, cyclophosphamide): Concurrent administration may increase the risk of bone marrow suppression.
- Penicillamine: Use with gold salts is not recommended due to an increased potential for hematologic and renal adverse effects.
- Theophylline and aminophylline: Decreased serum concentrations may occur; monitor clinical response if used together.
Side Effects & Overdose
Side Effects
Adverse effects of auranofin in dogs and cats are relatively common and are often dose dependent. Toxicities may involve the gastrointestinal tract, hematopoietic system, kidneys, liver, skin, and mucous membranes.
- Gastrointestinal effects: Diarrhea is the most frequently reported adverse effect, particularly in dogs. Signs are usually dose related and may resolve with dose reduction or drug discontinuation.
- Hematologic toxicity: Immune-mediated thrombocytopenia, hemolytic anemia, and leukopenia may occur. Discontinue auranofin and initiate corticosteroid therapy if immune-mediated reactions develop.
- Renal toxicity: Proteinuria may be observed; progression to clinically significant renal dysfunction is possible with continued therapy.
- Hepatic toxicity: Hepatotoxicity has been reported and may be identified through increased liver enzyme activity.
- Dermatologic and mucosal reactions: Dermatoses, including severe reactions such as toxic epidermal necrolysis, as well as corneal and oral ulceration, have been associated with auranofin therapy.
Overdose
Limited information is available regarding acute auranofin overdose in dogs and cats. Toxicity is expected to involve exaggerated gastrointestinal, hematologic, renal, hepatic, and neurologic effects.
- Acute toxicity: Based on laboratory and human data, large overdoses may result in neurologic signs, severe GI upset, and systemic toxicity.
- Initial management: Gastric decontamination may be considered following recent oral ingestion when clinically appropriate.
- Supportive care: Treatment is primarily supportive, including fluid therapy and monitoring of renal, hepatic, and hematologic parameters.
- Chelation therapy: Use of chelating agents (e.g., penicillamine, dimercaprol) is controversial and should be considered only in severe cases in consultation with a toxicology specialist.
- Consultation: For suspected or confirmed overdose, consultation with a 24-hour veterinary poison control center is strongly recommended.
Key Notes
Practical clinical considerations specific to auranofin therapy in dogs and cats, highlighting points not covered elsewhere:
- Delayed onset of effect: Therapeutic response may not be evident for several weeks, and lack of early improvement should not prompt premature discontinuation.
- Individual variability: Clinical response and tolerance vary widely between patients; dosing and continuation should be guided by both clinical signs and laboratory findings.
- Long tissue persistence: Gold has a prolonged tissue half-life, so adverse effects may persist even after the drug is discontinued.
- Monitoring commitment: Successful use requires strict adherence to scheduled laboratory monitoring and follow-up visits.
- Therapeutic expectations: Auranofin is rarely curative and is best viewed as a disease-modifying or adjunctive therapy.
- Cost considerations: Expense and the need for compounding should be addressed before initiating therapy to ensure owner compliance.
